Rotate an Ico sphere with 20 sides(Icosahedron) to align with the level grid
Create your Icosphere
Add a new Empty object
Turn on Face Snapping
Turn on the Align Rotation with Snapping Target option
Move the Empty object and press Ctrl while transforming to snap
Make it align to one of the desired faces
Afterwards select the Icosphere, then Shift-Select the Empty (so it stays the active object)
Press Ctrl+P to parent the Icosphere to the Empty
You can now move the empty freely wherever you want, and most importantly clear its rotation from the Toolshelf or with Alt+R
When correclty aligned unparent the Icosphere, and optionally apply its rotation if desired with Ctrl+A > Apply > Rotation